Heretofore, a method for manufacturing a three-dimensional shaped object by repeating forming a solidified layer by irradiating a powder layer formed of a powder material with a light beam, thereby allowing sintering or melting and subsequent solidification thereof to form a solidified layer, and then forming another solidified layer by newly forming a powder layer on the solidified layer, followed by irradiating the powder layer with the light beam, has been known.
In such a manufacturing method, there has been known a method using a forming device which comprises: a base which is fixed in order to improve an accuracy of machining a shaped object; a lifting/lowering frame which surrounds a circumference of the base and is freely capable of being lifted and lowered; a cover frame which has a window allowing transmission of light beam on its top surface, and whose bottom surface is opened, and which forms a chamber covering the powder layer by disposing it on the lifting/lowering frame (see Patent Document 1). In such a manufacturing method, a shaped object is formed by forming a powder layer and subsequently forming a solidified layer on a base, and repeating lifting up the lifting/lowering frame and stacking of solidified layers. In this way, the base on which the shaped object is mounted is fixed so as not to move, and as a result, the machining accuracy is improved.
However, in such a manufacturing method, the chamber is easily filled with fumes generated during sintering or melting and subsequent solidification, and fumes easily adhere to a window. An ambient gas is continued to be supplied into the chamber. However, it takes time to replace the fumes with the ambient gas, and a light beam scatters due to the filled fumes or the fumes adhering to the window, which has brought about the problem of decreased output and decreased degree of focusing of the light beam, and of deterioration in machining accuracy because of deterioration in positional accuracy of irradiation with the light beam. Further, there has been the problem that the light beam is absorbed into the fumes adhering to the window to raise a temperature of the window, which thermally deforms the window to further deteriorate the positional accuracy of irradiation.
Patent Document 1: JP-A-2009-7669